Not applicable.
1. Field of the Invention
The invention relates generally to downhole tools used to enlarge wellbores drilled in earth formations. More specifically, the invention relates to a fixed blade fixed cutter hole opener having an advanced cutting structure and gage configuration.
2. Background Art
Polycrystalline diamond compact (PDC) cutters have been used in industrial applications including wellbore drilling and metal machining for many years. In these applications, a compact of polycrystalline diamond (or other superhard material such as cubic boron nitride) is bonded to a substrate material, which is typically a sintered metal-carbide, to form a cutting structure. A compact is a polycrystalline mass of diamonds (typically synthetic) that are bonded together to form an integral, tough, high-strength mass.
An example of a use of PDC cutters is in a drill bit for earth formation drilling is disclosed in U.S. Pat. No. 5,186,268. FIG. 1 in the ""268 patent shows a cross-section of a rotary drill bit having a bit body 10. A lower face of the bit body 10 is formed to include a plurality of blades (blade 22 is shown in FIG. 1) that extend generally outwardly away from a rotational axis 15 of the drill bit. A plurality of PDC cutters 26 are disposed side by side along the length of each blade. The number of PDC cutters 26 carried by each blade may vary. The PDC cutters 26 are brazed to a stud-like carrier, which may also be formed from tungsten carbide, and is received and secured within a corresponding socket in the respective blade.
When drilling a wellbore, a PDC bit is attached to the end of a bottom hole assembly (BHA) and is rotated to cut the formations. The PDC bit thus drills a wellbore or borehole having a diameter generally equal to the PDC bit""s effective diameter. During drilling operations, it may be desirable to increase the diameter of the drilled wellbore to a selected larger diameter. Further, increasing the diameter of the wellbore may be necessary if, for example, the formation being drilled is unstable such that the wellbore diameter changes after being drilled by the drill bit. Accordingly, tools known in the art such as xe2x80x9chole openersxe2x80x9d and xe2x80x9cunderreamersxe2x80x9d have been used to enlarge diameters of drilled wellbores.
In some drilling environments, it may be advantageous, from an ease of drilling standpoint, to drill a smaller diameter borehole (e.g., an 8xc2xd inch diameter hole) before opening or underreaming the borehole to a larger diameter (e.g., to a 17xc2xd inch diameter hole). Other circumstances in which first drilling smaller hole and then underreaming or opening the hole include directionally drilled boreholes. It is difficult to directionally drill a wellbore with a large diameter bit because, for example, larger diameter bits have an increased tendency to xe2x80x9ctorque-upxe2x80x9d (or stick) in the wellbore. When a larger diameter bit xe2x80x9ctorques-upxe2x80x9d, the bit tends to drill a tortuous trajectory because it periodically sticks and then frees up and unloads torque. Therefore it is often advantageous to directionally drill a smaller diameter hole before running a hole opener in the wellbore to increase the wellbore to a desired larger diameter.
A typical prior art hole opener is disclosed in U.S. Pat. No. 4,630,694 issued to Walton et al. The hole opener disclosed in the ""694 patent includes a bull nose, a pilot section, and an elongated body adapted to be connected to a drillstring used to drill a wellbore. The hole opener also includes a triangularly arranged, hardfaced blade structure adapted to increase a diameter of the wellbore.
Another prior art hole opener is disclosed in U.S. Pat. No. 5,035,293 issued to Rives. The hole opener disclosed in the ""293 patent may be used either as a sub in a drill string, or may be coupled to the bottom end of a drill string in a manner similar to a drill bit. This particular hole opener includes radially spaced blades with cutting elements and shock absorbers disposed thereon.
Other prior art hole openers include, for example, rotatable cutters affixed to a tool body in a cantilever fashion. Such a hole opener is shown, for example, in U.S. Pat. No. 5,992,542 issued to Rives. The hole opener disclosed in the ""542 patent includes hardfaced cutter shells that are similar to roller cones used with roller cone drill bits.
There is a need, however, for a hole opener that makes use of recent advances in PDC cutter and blade technology. While PDC cutters have been used with, for example, prior art near-bit reamers, the PDC cutters on such reamers are generally arranged in a relatively simplistic fashion. This arrangement, among other factors, forms a relatively unreliable mechanical structure that is not durable, especially when drilling tough formations. Moreover, some prior art hole openers generate high levels of vibration and noise, and tend to cause the well trajectory deviate from the existing well trajectory. Therefore, it would be advantageous to produce hole openers with improved cutting structures.
In one aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades, and the at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. The plurality of cutting elements are arranged so that a net lateral force acting on the at least two blades is less than approximately 15% of an axial force applied to the hole opener.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. The plurality of cutting elements are arranged so as to substantially balance work performed by each of the at least two blades.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades, and the at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. The at least two blades are adapted to substantially mass balance the hole opener about an axis of rotation thereof.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. The plurality of cutting elements are positioned to each have a backrake angle different than about 20 degrees.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. The plurality of cutting elements comprises at least one cutting element having a diameter of at least one of 9.0 mm, 11.0 mm, 16.0 mm, 22.0 mm, and 25.0 mm.
In another aspect, the invention is a hole opener including a tool body comprising upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. Surfaces of the at least two blades are shaped so that a cutting element exposure is equal to at least a half of a diameter of the cutting element.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. At least one of the cutting elements on one of the blades is positioned so as to form a redundant cutting arrangement with at least one other one of the cutting elements disposed on a different one of the blades.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. The at least two blades and the tool body are formed from a non-magnetic material.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of the previously drilled wellbore. The at least two blades are formed from a matrix material infiltrated with a binder alloy.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. A perpendicular distance measured from a surface of the tool body to an outermost extent of a gage cutting element disposed on the at least two blades is equal to at least three times a diameter of the gage cutting element.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. The at least two blades comprise a diamond impregnated material. The at least two blades are adapted to increase a diameter of a previously drilled wellbore.
In another aspect, the invention is a hole opener including a tool body having upper and lower ends adapted to be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned substantially concentric with a wellbore when disposed therein. A plurality of cutting elements are disposed on the at least two blades. The at least two blades and the plurality of cutting elements are adapted to increase a diameter of a previously drilled wellbore. A pilot hole conditioning section comprising at least two azimuthally spaced apart pilot blades is formed on the tool body axially ahead of the at least two blades. The pilot blades are tapered toward a downhole end thereof. Gage pads positioned at selected diameters, and at least one cutting element is disposed on each pilot blade.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.